Fish - trawler disposing of contents into the drink (5)
I believe the answer is:
tetra
'fish' is the definition.
(tetra is a kind of fish)
'contents into the drink' is the wordplay.
'contents' becomes 'tr' (I can't explain this - if you can you should believe this answer much more).
'into' is an insertion indicator.
'the drink' becomes 'tea' (tea is a drink).
'tr' placed within 'tea' is 'TETRA'.
'trawler disposing of' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tetra that I've seen before include "... Four < , in composition" , "starter for four" , "Small brightly-coloured fish of aquariums" , "Denoting four (prefix)" , "This indicates a group of four" .)